A group of Chinese students living in western countries have issued a rare public appeal for their government to end its secrecy over the Tiananmen Square massacre and hold those responsible to account.

The open letter from 11 students enrolled at universities in the US, UK and Australia is politically risky at a time of tightening government controls on activists and rights groups, from small charities and feminists to human rights lawyers who take on politically controversial cases.

It prompted an angry attack from the hardline nationalist paper The Global Times, which accused the authors of serving “overseas hostile forces” and trying to “tear society apart”.

The lead signatory to the letter, Gu Yi, said the group felt they had a moral duty to share the information they had stumbled upon after leaving their home country, about the extent of the Tiananmen protests in Beijing and the bloody government crackdown on 4 June 1989.

Gu, a chemistry student at the University of Georgia, said: “I feel strongly as a Chinese citizen with full access to information outside China that I have a responsibility to tell my fellow citizens about this. We have been living in fear for a lot of years and what we are trying to do is fight this fear so we can live in freedom.”

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The lengthy discussion of what happened in May and June 1989 was mostly addressed to fellow students at home in China, trapped behind what the letter called the “ever higher internet firewall”, but pointedly criticised the government.

The letter said: “Some say the Communist party of China has taken lessens from 4 June and we should not pursue it anymore, and yet the repression lingers on: the truth is still being covered up; the victims are still being humiliated.”

It goes on to subvert the so-called China dream, a favourite slogan of the president, Xi Jinping, used by the government with a strict focus on economic progress.

“We have a dream in our hearts, that in the near future, on the basis of accurate history and the implementation of justice, everyone could live in a world free of fear. As a group of Chinese students overseas, this is our China dream.”

The letter has already drawn more than 50 new signatures since it was posted online, Gu said, including one from a high-school student in China whom he described as very brave. He had not told his own parents about the letter to prevent them worrying.

Its publication marked an unusual protest by students not connected to activist circles in China, and a generation below the activists who went into exile after 1989. The group are abroad for now, but choosing to post their open letter online so the message can reach China means its impact could follow them home as well.

Zhang Lifan, an independent historian and political commentator, said: “They could face difficulties when they get back to China and when they try to find jobs back home. Even their families could get into trouble.”

The events of 1989 are one of the biggest taboos in contemporary China, with the day’s bloodshed usually referred to simply as an “incident” in official media and government reports, and censors banning even indirect references.

“How risky is this letter? Given the shifting sands of political sensitivity, answering such a question is difficult, but the climate for discussing the events of 1989 has become much worse since the run-up to the 25th anniversary last year,” said Louisa Lim, the author of The People’s Republic of Amnesia, an account of the protests, the crackdown and the aftermath.

“In the past, private commemorations held behind closed doors had been tolerated; last year, these too were targeted ... The Chinese authorities seem determined to try to tamp down any discussion or commemoration of 4 June whatsoever using any means necessary.”

The Global Times insisted that the events at Tiananmen Square have been largely excised from public debate by common agreement rather than a government coverup. It said Chinese citizens who want to can easily bypass controls to access “sensitive information from overseas websites”.

“Chinese society has reached a consensus on not debating the 1989 incident,” said the broadside, originally published in Chinese and English. “When China is moving forward, some are trying to drag up history in an attempt to tear apart society. It’s a meaningless attempt.”

The Chinese government has been been extremely successful in controlling the awareness of events a quarter of a century ago, according to Lim.

China’s sophisticated, complex internet censorship system deploys a range of tools to manage the information its citizens see, from a firewall that cuts off access to undesirable foreign websites to groups of paid online commentators who bolster the government line and censorship of sensitive terms on domestic search engines.

Lim said: “The students who wrote this letter are correct to state that many of their contemporaries know very little about what happened on 4 June 1989.” She pointed out that even the iconic picture of a row of tanks halted by an unarmed man, referred to as tank man, is virtually unknown in China.

She said: “When I was writing my book, I asked 100 university students in Beijing to identify the picture of tank man. The vast majority, 85%, had no idea what it signified or where it was taken, asking questions like ‘Is it from South Korea?’ and ‘Is it in Kosovo?’”

“This is the demographic who are most likely to be able to ... bypass internet censorship, so I believe that outside Beijing and outside university campuses, the level of ignorance surrounding the Tiananmen crackdown is even higher.”

Despite the ferocity of the Global Times attack, Gu said he was grateful to the newspaper for drawing attention to a letter by 11 unknown students that might otherwise have languished in relative obscurity.

Originally posted online across a variety of state media, the Tuesday editorial drew attention to a petition that had previously gone unnoticed. The Chinese version was later stripped from all websites, but not before circulating widely enough that many stored versions can still be found.

Gu said: “The Global Times attacking our letter was the best advertisement. We think the fast removal of the letter shows they were confused in their response and that we had some impact in mainland China.”